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[ultrarnr]

So Saturday I am riding my 2014 SR the 67 miles from my Zero dealer to home. A few miles from home and I am down to 14% SOC and the power gets cut so I can only do 25 MPH. This happened once before and when it got down to 10% SOC it dropped immediately to 0% SOC and the bike died. So sure enough about 2 miles from home and as soon as the SOC reached 10% it immediately dropped to 0% SOC. Never fun to leave the bike on the side of the road and walk home. The cell balance in both cases was around 150 mV. It seems like when the cell balance gets to those levels the SOC shown is way off. But you have no way of knowing that while you are riding down the road. I have had full power (or at least able to go 55 MPH) at 6% SOC before. Have also had power cut at 9% SOC in which I could only go 45 MPH which quickly was reduced to 35 MPH. My experience is that once you get below 10% SOC it is questionable whether or not you will maintain power. But now after Saturday’s fun I am wondering about the risks of getting below 15% SOC. I am curious about the experiences of others out there and how their bikes reacted at lower SOC. At what point have you have power cut? 

[Richard230]

I ran my 2014 S down to 0% and it didn't show significant drop off in power until about the 2% level. However, I was riding on local streets at the time and was keeping my speed below 40 mph. The second the display showed 0%, the motor stopped.

[Electric Terry]

Sorry to hear ultra, there is definitely something about the 2014 state of charge algorithm that is too optimistic.  I had one cut out at 7% before going up a hill on me once, and I've heard many others mention this, so I know what you're talking about. 

On the 2015 models (and I assume the 2016's too) this algorithm is fixed.  You can easily run to 0% before losing power.  In fact a few weeks ago I was running around on purpose trying to drain the battery and test the supercharger.  I had to pick up a friend later from the airport.  There was an unexpected firmware compatibility issue with the new supercharger I was testing (which has since been fixed) and I was unable to charge.  I was able to make it from San Jose airport to Scotts Valley (28 miles) with 19% battery at highway speeds (with a passenger).  Although the final 9 miles from Summit Road on Highway 17 was at 0% on the dash.  When I dropped him off in Scotts Valley I still had good power and could quickly accelerate to 50 mph, although I could tell power was reduced a little.  I plugged in for about 3 minutes with the supercharger and rode back 7 miles to Santa Cruz with plenty of confidence.

Basically the point is with the 2014's it might be best not to rely on anything under 10%.  And if you do, have it be in a populated area where you can easily find a business or residence to ask to plug in for a few minutes to get to your destination if something happens.

I don't think anyone on a 2015 or now a 2016 has ever run out, have they?  I think I asked this before and no one has.  Hopefully the bikes are so good now that no one ever will.  But for those with Zero's 2014 and older, remember running out isn't the end of the world.  I did it quite a few times on my 2012 when I first got it.  Learned quickly just to look for the closest place with the lights on.  There is always an outlet somewhere.  Carrying a 25 ft extension cord doesn't hurt.

If your commute cuts it so close that you are down to 10%, using the new tax credit to upgrade to a 2016 with more energy density might be a great move.  Not just that but the leap in suspension and brakes from 2014 to 2015 was huge and worth it just for that!   

Although this isn't Zero's fault, congress seemed to forget about people who purchased an electric motorcycle in 2014.  If the new tax credit never got passed, I don't think it would be so apparent, but I see it.  And it just seems a little unfair.  It would be nice if Zero would offer an even more special upgrade deal to buy a 2016 for those who purchased a bike in 2014. 

[mrwilsn]

Although this isn't Zero's fault, congress seemed to forget about people who purchased an electric motorcycle in 2014.  If the new tax credit never got passed, I don't think it would be so apparent, but I see it.  And it just seems a little unfair.  It would be nice if Zero would offer an even more special upgrade deal to buy a 2016 for those who purchased a bike in 2014.

That would be awesome!  Even if they weren't matching the tax credit you would have gotten it would increase the total number of Zero's on the road and make a lot of loyal customers.

[ultrarnr]

Terry,

Thank you for the response, much appreciated. I really thought Zero had programmed some sort of "Limp Home Mode" in which power was intentially cut to preserve range. It was never consistant at which point power would be cut though and to what level. I am now wondering if everything is tied to the cell balance. I have known for awhile that going below 10% SOC was risky. But there are a lot of factors in power usage and sometimes a trip you have made multiple times with no problems suddenly has you at a much lower SOC than expected. For example I have learned about the impact of head winds the hard way and had to stop and charge because of them. But my most common long trip to going to North Hills Mall in Raleigh, NC and it is 65-70 MPH most of the way and multi-lane traffic. Having power cut suddenly so you go from 65 MPH to 25 MPH in heavy traffic is not always going to be survivable. Wonder way a software upgrade never happened.

Have been considering trading in for a 2016 SR since my 2014 SR warranty runs out the end of February. My 2014 SR has spent too much time in the shop since I got it and  hoping a 2016 is better. This experience makes that decision a lot easier.

On Saturday when I finally got my SR home I plugged it into 110 outlet, only 12:30 hours to fully recharge. Unplugged and then plugged my Elcons into the NEMA 6-50 outlet in my garage and it showed 2:02 hours till fully recharged. Interesting.

Thanks, Vinny

[Electric Terry]

Hey Vinny,

I know the area around Six Forks Rd very well.  I went to NC State and worked on Hillsborough St for 4 years.  I started a business converting cars so they wouldn't need to go to gas stations anymore and many of my customers were in the north Raleigh Area.

Cells can either be top balanced or bottom balanced but you can't do both as the cells don't have the exact exact exact capacity.
So if they are balanced at the top, 150mv or so between the highest and lowest seems pretty good at the bottom where the cell voltage is beginning to fall off a cliff.  That's basically 0.15 volts difference in cells where the voltage from 3.0v to 3.2v is less than a half percent, so I think that's pretty good.  I'll take a screenshot of mine next time I run it low.  Maybe others could too to compare, but I'm convinced that's normal.

Yes I think for you upgrading to a 2016 with more capacity would be a good idea.  One of the reasons for my last comment above about the tax credit.  Because I knew you got your bike in early 2014.  Perhaps also because of the issues you had in the shop, perhaps someone at Zero personally looking at your situation might be appropriate to see if anything can be done.  Probably not, but it would be something to hope for.  At least you could get a tax credit on a 2016 which is something to look forward to.

[Richard230]

When I ran my battery pack down to 0%, I was seeing as much as 240 mV difference between each group of cells.  But after 15 hours of charging and balancing the difference had dropped to 2 to 3 mV and that is what I still see with a 100% charge.  (My bike was assembled in December 2013.)

[grmarks]

The most I have seen on cell balance with my 2015 SR is 5 mV. 150 mV seems really high. Maybe this is the biggest factor in differing SOC cut backs?

[Electric Terry]

The most I have seen on cell balance with my 2015 SR is 5 mV. 150 mV seems really high. Maybe this is the biggest factor in differing SOC cut backs?

If you have seen this at less than 5% charge it would be so incredible I think it would be a first in history.  Check it the next time your pack is below 10% or so.  The lower you get the higher the difference will be.  I look forward to your response in a few days to see.  If you truly never get above 5% you have an amazing motorcycle!

[grmarks]

The most I have seen on cell balance with my 2015 SR is 5 mV. 150 mV seems really high. Maybe this is the biggest factor in differing SOC cut backs?

If you have seen this at less than 5% charge it would be so incredible I think it would be a first in history.  Check it the next time your pack is below 10% or so.  The lower you get the higher the difference will be.  I look forward to your response in a few days to see.  If you truly never get above 5% you have an amazing motorcycle!

Never checked it at 10% SOC, its never been lower than 17% SOC and I never checked it then. I thought that cell balancing only began at 95% SOC when charging

[grmarks]

Today it is at 80% SOC and cell balance is between 2 and 3 mV. I have never seen it less than 2 mV, so no change really. 20% use has resulted in 1 mV change so extrapolating it would be 7mV ( 2mV + 5mV (100% / 20% = 5)) at 0% SOC.
Of course extrapolating may be way off if things change more as it gets lower (not a linear line).

[ultrarnr]

grmarks,

Cell balancing begins as soon as you plug in your charger. On Saturday when I plugged in my SR I watched the app for several minutes. The cell balance began dropping immediately.  Vinny

[mrwilsn]

grmarks,

Cell balancing begins as soon as you plug in your charger. On Saturday when I plugged in my SR I watched the app for several minutes. The cell balance began dropping immediately.  Vinny

I think grmarks is talking about the BMS balancing function, which only occurs at the end of the charge cycle.  When you charge, the cells will naturally start to come back within balance of each other right away (as long as you don't have any bad cells).  At the end of the charge cycle the BMS uses the balance wires to ensure each cell is at the same voltage and will only charge the cells that need to be topped off, not charging the whole pack.  The BMS balancing is only required in order to get the cells to the very small tolerances you see when fully charged (2-5mV).  If you stop charging before the BMS balancing takes place you might still get within 20-30mV or better....others could probably comment better...my bike currently isn't connecting via bluetooth so I can't check on my bike right now.

[grmarks]

grmarks,

Cell balancing begins as soon as you plug in your charger. On Saturday when I plugged in my SR I watched the app for several minutes. The cell balance began dropping immediately.  Vinny

Because of my assumption (only balances after 95%) I have never bothered to connect my phone until it got to 95%, until yesterday. But yesterday didn't show any big change in cell balance.
   

[grmarks]

grmarks,

Cell balancing begins as soon as you plug in your charger. On Saturday when I plugged in my SR I watched the app for several minutes. The cell balance began dropping immediately.  Vinny

I think grmarks is talking about the BMS balancing function, which only occurs at the end of the charge cycle.  When you charge, the cells will naturally start to come back within balance of each other right away (as long as you don't have any bad cells).  At the end of the charge cycle the BMS uses the balance wires to ensure each cell is at the same voltage and will only charge the cells that need to be topped off, not charging the whole pack.  The BMS balancing is only required in order to get the cells to the very small tolerances you see when fully charged (2-5mV).  If you stop charging before the BMS balancing takes place you might still get within 20-30mV or better....others could probably comment better...my bike currently isn't connecting via bluetooth so I can't check on my bike right now.

OK I am confusing "cell balance" with "pack balance".
So cell balance is the cells joined in parallel to form modules (and give the required amp/h) that are then joined in series to make the pack voltage, correct?